The Xcode 13.4 image has been released and can be selected as follows:
macos:
xcode: 13.4.0
Thank you for your patience while we worked to overcome issues deploying these images out to our fleet 
VM Image Info
Xcode 13.4 Build version 13F17a is installed at /Applications/Xcode-13.4.app
The full manifest of installed software can be found here
Metal Image Info
Xcode 13.4 Build version 13F17a is installed at /Applications/Xcode-13.4.app
The full manifest of installed software can be found here